Adaptive optics systems implemented using two-dimensional phase retrieval and a microelectromechanical deformable mirror

Abstract

We present a fast 2-D phase retrieval approach used to per- form optical phase modulation of a microelectromechanical-deformable mirror (MEM-DM). Traditional solutions to beamsplitting, beam steering, and beam shaping (BS 3 ) involve multiple and sometimes costly optical components. For example, beamsplitting is normally accomplished with beamsplitters, beam steering is normally achieved with gimbaled me- chanical devices, and beam shaping is normally done with addressable, polarized, and potentially absorptive devices such as LCDs. Using the phase retrieval algorithm with a desired far-field amplitude pattern as a constraint, a segmented wavefront control device is shown to simulta- neously perform the functions of BS 3 . The MEM-DM used is a foundry- microfabricated device that is attractive for optical phase modulation ap- plications primarily because of its inherent low cost and low drive voltages. The MEM-DM shapes the beam based on the results of a modified Fienup and Roggemann/Lee phase retrieval algorithm imple- mented within the system. The optical bench setup and the experimental results for BS 3 are presented. Measured experimental data show good agreement with model simulations. A comparison between analog MEM- DMs and a digitally controlled MEM-DM is presented. Overall, experi- mental results demonstrate the efficacy of the phase retrieval algorithm and a single phase control device in solving optics problems normally solved through traditional techniques and multiple devices. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)02310-2)